The present invention relates to optical disc drives and, more particularly, to a mechanism and method for securing and covering the optical pickup unit of an optical disc drive when the optical disc drive is not in use.
Optical disc drives are devices that use light to translate information stored on an optical disc to a machine-readable format, e.g., binary data. Examples of optical disc drives are known in the art as compact disc drives (often referred to simply as CDS) and digital versatile disc drives (often referred to simply as DVDs). Some optical disc drives have the additional capability of being able to write data onto an optical disc by the use of a light source, e.g., a laser. Optical disc drives are being used in various applications including music and video playing and recording devices and computer data storage devices. As these applications become more portable, the optical disc drives also need to become more portable. For example, they must be compact and able to withstand the shock and vibration to which portable applications are commonly subject.
The optical disc is a round, flat device similar to a record. Digital data is stored in spiral tracks on the optical disc in much the same way analog audio information is stored in a spiral groove on a record. The data stored on an optical disc, however, is much more compact than the audio information stored on a record. For example, the radial distance between tracks on an optical disc is typically approximately 1.6 microns for a compact disc and less for a digital versatile disc. The data on the optical disc consists of a plurality of optical transitions that are detected or xe2x80x9creadxe2x80x9d by the optical disc drive as the optical disc spins. The optical disc may spin at varying speeds of up to 4000 rpm as data is being read from or written to the optical disc.
A schematic diagram of a side view of a conventional optical disc drive 400 is illustrated in FIG. 1. The optical disc drive 400 is illustrated with an optical disc 190 attached thereto wherein data is stored on an optical surface 192 of the optical disc 190. The optical disc drive 400 has three basic components, a drive motor 420, an optical pickup unit 414, and an optical mechanical assembly 408. The drive motor 420 serves to spin the optical disc 190 at predetermined rates that typically vary from several hundred to several thousand rpm. The optical pickup unit 414 serves to read and write data from and to the optical surface 192 of the optical disc 190. The optical mechanical assembly 408 serves to move the optical pickup unit 414 in a radial direction 440 relative to the optical disc 190 to predetermined locations relative to the optical disc 190.
The optical pickup unit 414 typically has a laser, not shown, to illuminate the optical surface 192, an objective lens 416 to focus the laser, and a photodetector, not shown, to translate light to machine-readable data. Other optical components may be located within the optical pickup unit 414 to direct light between the photodetector and the objective lens 416. Mechanical components may be located in the optical pickup unit 414 and may serve to support the objective lens 416 and to move the objective lens 416 relative to the optical pickup unit 414.
The optical pickup unit 414 emits incident light that is directed through the objective lens 416 and to the optical surface 192 of the optical disc 190. The optical pickup unit 414 may, as an example, output approximately 20 milliwatts of coherent light having a wavelength of approximately 790 nanometers. Light is reflected from the optical surface 192 of the optical disc 190 through the objective lens 416 and back to the optical pickup unit 414. The light reflected from the optical surface 192 of the optical disc 190 varies in intensity wherein the variations are caused by light reflecting from the optical transitions on the optical surface 192 as the optical disc 190 spins. These variations in intensity are representative of the data stored on the optical surface 192.
As the optical disc 190 spins, the mechanical components in the optical pickup unit 414 move the objective lens 416 in a radial direction 440 and a normal direction 430. Specifically, the optical pickup unit 414 moves the objective lens 416 normal to the optical surface 192 of the optical disc 190 to focus light between the optical surface 192 and the optical pickup unit 414. This focusing allows a sharp image of the optical transitions on the optical surface 192 to be focused onto the photodetector, which improves the operation of the optical disc drive 400. The optical pickup unit 414 moves the objective lens 416 radially relative to the optical surface 192 of the optical disc 190 to follow the tracks on the optical disc 190 as the optical disc 190 spins. This movement of the objective lens 416 is very fine because the objective lens 416 has to follow the tracks with a tolerance of approximately one micron in the radial direction 440 as the optical disc 190 spins. The objective lens 416 is generally mounted to the optical pickup unit 414 by the use of very delicate components. This delicate mounting is required in order for the objective lens 416 to move as precisely as is required to follow the tracks on the spinning optical disc 190 and to focus the optical transitions from the spinning optical disc 190 onto the photodetector.
As described above, the objective lens 416 has to move very precise distances in very short periods in order to follow the tracks on the optical surface 192. This makes the optical pickup unit 414 a relatively delicate device. The fragile nature of the optical pickup unit 414 makes it susceptible to failure due to relatively mild shock or vibration. One cause of failure is due to the objective lens 416 becoming dislodged from the structural components in the optical pickup unit 414 that secure the objective lens 416 to the optical pickup unit. Another cause of failure is due to the components that move the objective lens 416 becoming damaged. These problems are more prevalent in optical disc drives used in portable devices because these optical disc drives are typically subjected to greater and more frequent shock and vibration.
Additional problems occur in optical disc drives that have the objective lens 416 exposed to a user when an optical disc 190 is being exchanged from the motor 420. For example, a user may inadvertently touch the objective lens 416, which may damage the optical pickup unit 414 or contaminate the surface of the objective lens 416 with oils from the user""s skin. The user may also cause the optical disc 190 to contact the optical pickup unit 414, which could damage the optical pickup unit 414 or the objective lens 416. In addition, during the exchange of the optical disc 190, the optical pickup unit 414 becomes exposed to the environment and may become damaged if contaminants from the environment enter it. An exposed optical pickup unit 414 may also be dangerous to the user if the optical pickup unit 414 becomes active in the presence of a user. Laser light is typically emitted by the optical pickup unit, which is a relatively bright and narrow beam of coherent light. This light may pose health risks to the user, such as causing irreversible and permanent damage to the user""s retinas.
Therefore, a need exists for a mechanism incorporated into an optical disc drive that will secure the optical pickup unit in a fixed position and out of sight and reach of a user when the optical disc drive is not in use.
An optical disc drive having a cover member movably attached thereto that secures and protects an optical pickup unit is disclosed herein. The optical disc drive is a device that spins an optical disc and xe2x80x9creadsxe2x80x9d data from the spinning optical disc in a similar manner as a magnetic disc drive reads data stored on a magnetic disc. Some optical disc drives are also capable of xe2x80x9cwritingxe2x80x9d data to an optical disc. The optical pickup unit is a component of the optical disc drive that actually reads data from or writes data to the optical disc. The optical pickup unit typically emits a narrow beam of coherent light through an objective lens to illuminate the optical disc. The light may, as an example, be emitted by a laser. Light reflected from the optical disc passes through the objective lens and to a photosensing device where it is translated to machine-readable data, e.g., binary data. The optical pickup unit may move on an axis so as to read and write data on specific portions of the optical disc.
The cover member may be movably attached to the optical disc drive wherein the cover member has a first operating position and a second operating position. When the cover member is in the first operating position, it may be positioned so as not to block the light path between the optical pickup unit and an optical disc. When the cover member is in the second operating position, it may be positioned so as to block the light path between the optical pickup unit and the optical disc drive. Positioning the cover member in the second operating position is used when the optical pickup unit is likely to be exposed to a user, such as when a user is replacing the optical disc. This placement of the cover member in the second operating position may prevent a user from contacting the optical pickup unit, thus, preventing the user from damaging the optical pickup unit. This placement of the optical pickup unit may also prevent a user from being exposed to harmful laser emissions from the optical pickup unit should the optical pickup unit become active during the period that the user is exposed to the optical pickup unit.